Multiple pitch self-cleaning belt pulley

ABSTRACT

The invention pertains to a pulley for belt conveyors, particularly belt conveyors used in the conveying of stones, gravel, and the like wherein the pulley structure is self-cleaning of foreign matter received within the confines of the pulley to prevent belt damage. The pulley consists of a plurality of helically disposed webs spiralled about a rotatable shaft. A plurality of webs are defined upon the shaft on each side of the pulley central region wherein at least two separate webs define a set of multiple pitch helices, and each set is spiralled about the axis of rotation in an opposite direction wherein foreign matter received between the webs is moved to the pulley ends in a self-cleaning manner. A disc is utilized at the pulley central region to which the inner ends of the web sets are affixed and the periphery of the webs is of a greater axial dimension than the web plate to increase the belt surface loading area. The use of a plurality of helices in each web set increases the locations of belt engagement and support without detracting from the self-cleaning function.

REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of Ser. No. 746,304 filedDec. 1, 1976, now abandoned.

BACKGROUND OF THE INVENTION

The invention pertains to self-cleaning pulleys for belt conveyorsystems utilizing helically spiralled belt supporting webs.

Belt conveyors are widely used in the bulk handling of material whichmay consist of a plurality of hard particles such as stones, rocks, coaland the like. A typical belt conveyor used in the stone and gravelprocessing art, for instance, would include a motor driven upper drivepulley, a lower idler or tail pulley, and a flexible belt passing overthe drive and tail pulleys usually supported intermediate the pulleys bya belt guide or auxiliary rollers which permit the conveyor to form aconcave configuration to maintain the material upon the belt.

Such conveyors are usually inclined at a relatively steep angle to thehorizontal and due to the vibration of the conveyor and the movement ofthe rock and gravel particles thereon it is not unusual for rocks andstones to fall from the conveyor at a point above the tail pulley. Suchmatter falling from the conveyor will often engage the inner sides ofthe return portion of the conveyor belt which is travelling downwardlytoward the tail pulley, or the particle may fall directly into theregion of the belt conveyor at the tail pulley, and in such instancesthe particle may become wedged between a conventional tail pulleysurface and the belt. The presence of the particles between the pulleyand the belt will stress the belt at a localized point often cutting orripping the belt, and may possibly damage the pulley. Additionally, suchan occurrence may cause misalignment of the belt on the pulley causingthe belt to be thrown.

The aforementioned problems can be partially controlled by utilizingshields and pulley baffles, but such devices are troublesome and requireconstant maintenance and adjustment, and are easily damaged.

Another approach to solving the aforementioned problem has been the useof self-cleaning pulleys utilizing helical webs spiralled in oppositedirections from the central region of the pulley wherein foreign matterreceived within the pulley is conveyed from the pulley ends, and suchdevices, while patented, have not achieved commercial success. Suchself-cleaning pulleys are shown in U.S. Pat. Nos. 2,886,168, Calder, and3,626,773, Loeffler, and British Pat. No. 810,804. However, suchpatented devices have the disadvantage of only supporting the conveyorbelt at a single point at any axial location on the pulley resulting inhigh conveyor belt loads at the location of pulley engagement therewith,and such patented devices do not provide adequate support of the beltconveyor at the pulley central region and ends.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a pulley for belt conveyorsystems which is self-cleaning in operation whereby foreign particlesentering the confines of the pulley are axially translated from thepulley configuration.

A further object of the invention is to provide a self-cleaning pulleyfor use with conveyor belts wherein the pulley consists of a pluralityof helical webs coaxially disposed about an axis of rotation, aplurality of helical webs defining a set being associated on each sideof the pulley central region producing a multiple pitch helices whichprovides at least two belt engaging locations at each pulley axiallocation resulting in superior belt supporting characteristics andreduced belt and pulley loading forces.

An additional object of the invention is to provide a self-cleaningpulley for use with conveyor belts utilizing a plurality of helical websat each axial location of the pulley from the pulley central region, thediameter of the webs adjacent the central region being greater than theweb's diameter at the pulley ends whereby the pulley is crowned tofacilitate centering of the belt thereon during operation.

A further object of the invention is to provide a self-cleaning pulleyfor use with conveyor belts wherein a plurality of intermeshed helicalwebs are utilized upon each side of the pulley central region to providea plurality of helical sets, and the pulley central region includes acircular disc to which the inner ends of the webs are affixed, and whichalso includes a belt supporting periphery at the central regionthroughout the pulley's circumference.

In the practice of the invention the pulley is defined by a rotatableshaft having a plurality of webs helically mounted thereon in a spiralmanner. The webs include an inner edge affixed to the shaft, and anouter edge which defines a belt engaging periphery. The outer edge isprovided with a band of an axial width greater than the thickness of thewebs to reduce belt loading pressure, and the webs on opposite sides ofthe pulley central region are spiralled in opposite directions whereinforeign matter received within the webs is axially translated from thecentral region for self-cleaning purposes, and equalized belt engagingforces are produced by the pulley to maintain the belt centered thereon.

A significant feature of the invention lies in the fact that a multiplepitch web is utilized on each side of the pulley central region. Thismultiple pitch web is produced by using a plurality of webs, at leasttwo, having a relatively large pitch whereby one web may be locatedintermediate the other to define a double helices, the double helicestogether defining a helical set. The sets on opposite sides of thecentral region spiral in opposite directions about the shaft axis, andthe use of the double helices results in at least two pulley peripherallocations capable of belt engagement for each pulley axial location.

The presence of the circular disc at the pulley central region assuresuniform engagement and support of the belt at the central regionimproving the belt running characteristics without sacrificing any ofthe self-cleaning aspects of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The aforementioned objects and advantages of the invention will beappreciated from the following description and accompanying drawingswherein:

FIG. 1 is an elevational view of a pulley in accord with the invention,partially sectioned, and illustrating a conveyor belt disposed thereon,

FIG. 2 is an end elevational sectional view of the pulley as taken alongSection II--II of FIG. 1,

FIG. 3 is an elevational sectional view taken adjacent the pulleycentral region along Section III--III of FIG. 1,

FIG. 4 is an elevational sectional view as taken through a web set alongSection IV--IV of FIG. 1, and

FIG. 5 is a detail, cross sectional, diametrical view of a portion of aweb set in accord with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As will be appreciated from FIG. 1, a self-cleaning pulley in accordwith the inventive concepts includes a cylindrical shaft assembly 10rotatably supported upon bearings 12. The pulley would normally beutilized as a tail or idler pulley about which a flexible conveyor belt14 passes in changing direction. In most gravel processing systems thetail pulley will be located at the lower region of the belt conveyorwherein a motor driven drive pulley, not shown, located at the upper endof the belt conveyor system provides the power to translate the belt 14.Accordingly, the bearings 12 would normally be of the anti-friction typemounted in side rails 16 of the belt conveyor apparatus, and the pulleyis rotated solely by the rotative force imposed upon the pulley by thebelt.

In a commercial embodiment of the invention the shaft assembly 10includes an inner shaft 18 which is journaled within the bearings 12 andthe outer hollow shaft 20 concentrically circumscribes the shaft 18 andis coaxially affixed thereto by sleeve end caps 22. The end caps 22 mayincorporate known bushing structures for accurately concentricallylocating the shaft 20 upon the shaft 18, and this particular bushingstructure constitutes no part of the present invention.

The belt supporting structure of the pulley comprises a central disc 24affixed to the shaft 20 at its central region and web sets generallyindicated at 26 and 28. A web set is located upon each axial side of thecentral disc 24 and the web sets are identical in configuration exceptthat they are mirror images of each other, web set 26 being spiralled ina "right hand direction" while web set 28 is helically spiralled in a"left hand direction" about the axis of shaft 20.

In the illustrated embodiment each web set consist of two helical websformed of plate material of substantial pitch whereby one web of the setmay be located within the helices of the other web to form a doublehelices similar in concept to a double thread. Web set 26 consists ofwebs 30 and 32, and set 28 consists of webs 34 and 36.

Each web includes a radial portion 38 formed of plate material, such asone-eight inch steel plate which is of a continuous smooth configurationthroughout its radial and axial length. Each web also includes an inneredge 40 which is welded to the shaft 20, and the webs also include anouter edge which constitutes a belt supporting surface. The outer edgesare defined by a rim or band 42 of a rectangular cross sectionalconfiguration as will be appreciated from FIG. 4, and the axial width ofthe bands 42 is significantly greater than the thickness of the webplate 38 wherein the periphery of the web is of a T-shaped crosssectional configuration. The bands are preferably welded to the webplate outer portion, and the axial dimension of the band 42 is such asto significantly reduce the area loading pressures imposed on the beltby the pulley in order to achieve greater belt life and better beltrunning characteristics.

In the interest of belt running characteristics it is also desirablethat the pulley be "crowned" and in this respect the diameter of thewebs gradually increases from the pulley ends as generally indicated at44 and 46 to the central region disc 24, as will be appreciated fromFIG. 1.

The central region disc 24 is of a circular configuration as will beapparent from FIG. 3, and a band 48 is welded to the circular peripherythereof wherein the maximum diameter of the pulley is defined by thedisc, and, at its center, the pulley is provided with a 360° beltsupporting surface, which significantly improves the belt runningcharacteristics as compared with known self-cleaning pulleys.

The inner end 50 of the web 30, and the inner end 52 of the web 32, aswell as the inner ends of the webs 34 and 36 of set 28 are disposedadjacent the central disc 24, and are preferably welded thereto, andthis fabrication insures high strength support of the inner ends of thewebs, while also strengthening the central disc.

As will be appreciated from FIG. 2, the outer ends of the webs 30 and 32are represented at 54 and 56, respectively, and these edges aretangential to the shaft 20. The use of a plurality of webs in each setpermits the belt edges to be supported at two locations, at least duringa portion of the pulley rotation, and the plurality of webs within a setprovides superior belt support adjacent the pulley ends 44 and 46 ascompared with self-cleaning pulleys having only a single spiral web.

As will also be appreciated from FIG. 4, at any plane taken at rightangles to the shaft axis, as represented by Section IV--IV, such a planewill intersect the web's peripheral band 42 at two locations at 180°intervals constituting a plurality of support points of the belt duringpulley rotation at each pulley axial location, and such use of aplurality of helices in each web set provides significantly greater beltwear and improved running characteristics over single web self-cleaningpulleys.

In operation, the belt 14 will normally be driven in a single directionduring conveying. Reversal of the direction of belt movement is unusual,and would occur only for a few or partial pulley rotations that might beneeded to repair the belt or otherwise clear the machine. As viewed inthe drawings, the direction of normal pulley rotation is clockwise, asindicated by the arrows.

During operation, gravel, rocks, stones and foreign matter falling uponthe return portion 58 of the belt 14, FIG. 2, may enter the radialconfines of the web sets 26 and 28. However, because of the spacingbetween the helices of a web set the rocks, stones, etc. will be locatedbetween the helices, rather than between the belt engaging band 42 andbelt 14, and the direction of spiral of the webs will axially translatethe foreign matter toward the nearest pulley end. Thus, thisself-cleaning action of the pulley permits even relatively large amountsof foreign matter to be quickly cleared from the pulley, and the factthat the web sets are of a multiple pitch will cause an axialdisplacement of the foreign matter considerably faster than occurs whena single helical web is used.

In the disclosed embodiment the web sets 26 and 28 each consist of twowebs to define a double helices. It is within the concept and scope ofthe invention that a web set could consist of three, four or morehelices, each web having an inner end disposed adjacent the central disc24, and an outer end disposed adjacent a pulley end 44 or 46. Forinstance, with a triple helices, at each axial location of the pulleythree belt engaging locations will exist disposed at 120° intervals, andin a quadruple helices web four belt engaging locations exist for eachpulley axial location disposed at 90° intervals about the shaft axis.Such three and four web sets have the advantage of providing even morebelt supporting locations per axial segment than a two web set, but itwill be appreciated that the advantages of such a higher number of webper set with respect to belt supporting capabilities is offset by highermanufacturing costs and a reduction in the axial spacing betweenadjacent webs as to accommodate large stones or rocks which may fallinto the pulley.

It is appreciated that various modifications to the inventive conceptmay be apparent to those skilled in the art without departing from thescope of the invention.

I claim:
 1. A pulley for a belt conveyor or the like adapted toprimarily rotate in a given direction about a longitudinal axis andcharacterized by its self-cleaning and belt supporting abilitycomprising, in combination, a shaft defining an axis of rotation, saidshaft including first and second ends and a central region intermediatesaid ends, a plurality of radially disposed webs formed of platematerial helically circumscribing said shaft, said webs each includingan inner edge disposed adjacent said shaft and an outer edge radiallyspaced from said shaft, at least two webs extending from said centralregion to said first end constituting a first web set and at least twowebs extending from said central region to said second end constitutinga second web set, the webs of a set being helically disposed about saidshaft in a common direction and each web having an inner end located atsaid central region and an outer end located adjacent a common shaftend, said webs of a set being interspaced between each other defining amultiple helix wherein a plane at right angles to said shaft axisintersecting a web set intersects at least two web outer edges, the websof said first set being helically disposed about said shaft in adirection opposite to that of the webs of said second set and in such adirection relative to said given direction of pulley rotation thatforeign matter within a web set is axially translated in a directionfrom said shaft central region toward a shaft end for discharge from theweb at a shaft end, a circular disc affixed to said shaft central regionlying in a plane substantially perpendicular to said shaft axis, saiddisc having an outer edge defining a diameter substantially equal to thediameter of said webs' inner ends constituting a belt supportingperiphery and said webs' inner ends terminating at said disc, said webs'and disc's outer edges constituting a belt supporting periphery andbeing of an axial dimension greater than the thickness of the platematerial forming said webs and disc.
 2. In a pulley for a belt conveyoras in claim 1, the radial spacing of said webs' outer edge from saidshaft being greater at said webs' inner ends than at said webs' outerends whereby said webs' outer edges define a crown at the shaft centralregion and disc.
 3. In a pulley for a belt conveyor as in claim 1wherein said webs' inner edges are welded to said shaft.
 4. In a pulleyfor a belt conveyor as in claim 1 wherein said webs' inner ends areaffixed to said disc.
 5. In a pulley for a belt conveyor as in claim 1,wherein said webs' and disc's belt supporting periphery is defined by aband affixed to said webs' and disc's outer edge, said band having awidth in the axial direction of said shaft greater than the thickness ofsaid web plate material whereby said webs' and disc's outer edge is of aT-shaped transverse cross section to minimize belt wear and reduce thebelt surface area loading pressure at belt contact.